This invention relates to compact primers of the type used, for example, with personal computers, wherein the computer produces a stream of binary electrical signals to control the printer to print typed and graphic output. In particular it relates to a compact, portable printer of this class--that is, a signal-activated printer of this general size and print capacity--having a relatively simple mechanical structure and high performance.
Presently, the design of primers of this type is very much influenced by economics, with the result that there have evolved a small number--illustratively two, although there is room for argument--of general classes of such devices. One of these classes consists of machines that sell for about one to five thousand dollars. This class includes machines such as laser printers, that form a dielectric latent image on a photoconductive drum, tone the latent image and transfer the toned image to paper, on which the image is subsequently fused. This class of printer borrows various ones of its image-forming steps or mechanisms from the field of photocopiers or electrographic printers, and thus tends to involve many parts that wear, require adjustment and add cost both to the initial price and to required maintenance of the machine. However, the basic technology is quite mature, and the basic consumable toner component is cheap. These printers are capable of relatively high speed and high quality imaging.
The second general class consists of rather simpler devices, such as ink jet or bubble jet primers, which cost well under one thousand dollars and employ a printhead to directly form the image on a sheet as it is fed through the device. Such devices can be made quite small since they require neither hot fusing stations nor lengthy optical paths, and they can be made quite simple since only a single mechanical coordinating coupling is required, namely that between the sheet advance roller and the print head cross-scan carriage. Moreover, this latter mechanism can be eliminated by using a full page width ink jet head. Other devices of equally simple construction are also available, such as thermal or impact printers, but these tend to require expensive disposables, such as special thermal paper or inked ribbons, and they may produce a decidedly inferior image. However, although simple and initially cheap, ink and bubble jet printers of this second class each have their own limitations in terms of lifetime, failure rates, cost of disposables or, most commonly, printing speed or capacity.
It would therefore be highly advantageous if a printer design could achieve the size and simplicity of this latter class of instruments while employing the well developed and high quality imaging processes of the first class mentioned above. In particular, a simple printer employing toner imaging processes would offer great advantages.